The present invention relates generally to phase dividers, and more particularly to a frequency divider for quadrature signals.
In synchronous detectors for M-ary phase shift keyed signals, a series of an M-th power multiplier, a low-pass filter and a 1/M frequency divider is connected to the output of an A/D converter to recover the transmitted carrier for synchronously detecting the original signal. The 1/M frequency divider comprises an xy-to-8 (phase) conversion table which detects the phase angle of quadrature (complex) signals from the A/D converter and supplies it to a phase divider that divides the detected phase angle with a ratio 1/N. The output of the phase divider is coupled to a sine translation table and a cosine translation table to generate cosine (real part) and sine (imaginary part) wave signals. The phase .theta..sub.i of the input signal to the 1/M frequency divider is defined within the range between -.pi. and +.pi.. If there is a phase change of 2.pi., the input phase can be represented as .theta.'.sub.i =.theta..sub.i +2.pi.. However, the phase conversion table cannot discriminate between .theta.'.sub.i and .theta.".sub.i and treats the input phase equivalently as .theta.".sub.i =.theta..sub.i (mod 2.pi.). Under such circumstances, the division by the phase divider results in a phase angle .theta.".sub.i /M=.theta..sub.i /M. Since it must be .theta.'.sub.i /M=.theta..sub.i /M+2.pi./M, a phase error of 2.pi./M results.